Cemented carbide



Patented May 22,1934 I common CARBIDE Floyd 0. Kelley, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York NbDrawing. Application February 14, 1931, Serial No. 515,899

3 Claims. (01. 75-1) The'present invention relates to cemented cartionwhich, although somewhat brittle, may be bldes but more particularlyto'a sintered compoemployed with satisfactory results as a tool bitsition consisting mainly of tantalum carbide and for cutting steel orlike materials. If desired, the columbium carbide in combination with abinder powdered material after it is pressed may be fired 5 materialhaving alower melting point than either in a closed graphite tube forabout one half-hour of theecarbides. at a temperature of about 800 C. to1100 C., then 60 In my priorapplication Serial No. 478,557, filedshapedor cut-to the desired size and then fired as August 28, 1930, I.have disclosed and claimed a usual in the closed graphite tube at atemperature combination of tantalum carbide withv a binder of about 1400C. to 1600 C.

0 material and in my prior application Serial No. When employed as atool bit the cemented 496,826, filed November 19, 1930, I have disclosedcarbide is usually copper brazed to a steel shank. and claimed aplurality of carbides, for example I have found it desirable to employ aflux, such as tantalum carbide and tungsten carbide in combiborax, inthe brazing operation in order to secure nation with a binder material.The tantalum a good joint between the shank and the bit.

carbide employed in the compositions disclosed in With a compositionconsisting of about 13% my prior application is manufactured fromsubcementing material and the remainder tantalum stantially puretantalum. Thelatter, however, is carbide and columbium carbide, variousproporquite expensive to produce due to the fact that it tions of thecarbides may be employed. For exis very dimcult to remove columbiumwhich is an ample, I have employed about 5% to 40% columimpurityoccurring in varying quantities in tan.- bium carbide with 82% to 47%tantalum carbide, talum ore. V the smaller percentages of columbiumcarbide It is one of the-objects of the present invenbeing associatedwith. the higher percentages of tion to provide an improved cementedcarbide tantalum carbide and vice versa, the total carcompositioncontaining not only tantalum carbide content of the composition in anycase bide but columbium carbide as the main ingreamounting to about 87%.t

V dients thereof. The modulus of rupture of a tool bit employing Whilethe present invention will be illustrated 13% of a cementing mediumconsisting of about in connection with a composition consisting of 37%molybdenum and about 63% iron and havabout 13% binder material and about87% of a ing the lowest content of columbium carbide spew mixture oftantalum carbide and columbium carcified above (5%) and'the highestcontent of hide, the invention is not restricted to these spetantalumcarbide (82%) is about 71,000 pounds ciflc proportions of materials. Ifdesired, I may per square inch and the Rockwell A hardness employ fromabout 3% to about binder maabout 88.2. A tool bit employing the sameperterial in the composition. centage of the same cementing medium andcon- According to the present invention, tantalum taining the highestcontent of columbium carcarbide and columbium carbide in suitableprobide (40%) and the lowest content of tantalum portions are groundin aball mill for about four carbide (47%) has a modulus of rupture of abouthours or until the powdered material is capable 80,000 pounds per squareinch and a Rockwell 01 passing through a 325 mesh screen. The hardnessof about 87.8.

4 mixed carbides are then ball milled with an ap- With tool bits of thesame weight, it will be preciable quantity of cementing material forexfound that the volume of the tool bits increases ample powdered ironand molybdenum which towards the columbium carbide rich endof the havebeen ground to a suitable degree of above series, 1. e. a tool bitcontaining 40% columflnenes's. The mixed powdered materials are thenbium carbide and 47% tantalum carbide has 5 ground in the ball mill forabout four hours or more than twice the volume of a tool bitcontainuntil they are capable of passing through a 325 ing 5% columbiumcarbide and 82% tantalum mesh screen, The powdered mixture thusobcarbide. tamed is pressed to a desired shape in a hydraulic Thepresent invention is not limited to the use press, the pressure employedbeing about to of any particular cementing material. Metals of 50 tonsper square inch; The pressed material, the iron group taken alone ormetals of that which may be handled easily, is fired in a closed groupin combination with metals of the 6th a graphite tube in a hydrogenfurnace at a temgroup of Mendelejeffs periodic table of elementsperature of about 1400 C. to 1600" C. for about may be employed as thebinder material. I have 1% hours. At'this temperature the pressedmafound that the binder material. consisting of as terial is sinteredinto a hard metallic composiabout 37% molybdenum and about 63 parts ironno is a very satisfactory one for a mixture of tantasection and testedon a 3 nickel steel log hav-' ing a Brinnell hardness of 219 ran for 29minutes with a feed of 25/1000pf an inch, a depth of cut of 1% of aninch and a speed of 180 feet per 11 ute. The tool produced anunusuallysmooth finish on the steel log. Without regrinding and with thesame feed and cut, the speed was increased to 200 feet per minute. Thetool was op-'-' erated under these conditions for eleven minutes withoutany sign of breakdown of the tool. It

showed no signs of wear, retained its sharp cutting edge and was inexcellent condition at the end of the test.

Ordinarily, with the particular kind of work specified above and withthe feed and cut indicated, it would be extremely difllcult, if notimpossible, for a motor to turn a lathe ata speed of 200 feet perminute. However, with the cemented carbide tool described above themotor easily operated the work at a speed 01 200 feet per-minuteprobably due to the unusually sharp cutting edge on the tool and also tothe low coeficient of friction between the tool and the work.

WhatI claim as new and desire to secure by Letters Patent 01' the UnitedStates, is:

1. I A sinteredcomposition containing about 3% to about 25% of acementing medium, the remainder of said composition consistingsubstantially of tantalum carbide and columbium carbide, the columbiumcarbide comprising'not appreciably more than 45% 01' 'said composition,

said cementing medium containing an appreciable quantity but not morethan 50% of a metal or the 6th group of Mendelejefls periodic table ofelements, the remainder of said cementing medium consistingsubstantially of metal of the iron group.

2. A sintered composition containing about 3% .to about 25% ot acementing medium, the remainder of said composition-consistingsubstantially of tantalum carbide and columbium carbide, the'columbiumcarbide varying from a few percent up to about 45% -of said composition,

said cementing medium containing an appreciable. quantity but not morethan 50% of a metal of the 6th group, the remainder of said cementingmedium consisting of metal of the. iron group.

3. A sintered composition containing about 3% to about 25% of acementing medium, the remainder of said composition consistingsubstantially of tantalum carbide and'columbium carbide, the columbiumcarbide varyin from a few per cent up to about 45% of said composition,said cementing medium consisting mainly ofa metal of the iron group.

FLOYD c. KELLEY.

